Articles de revues : « CTBNC »

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Linzner, Dominik, et Heinz Koeppl. « Active learning of continuous-time Bayesian networks through interventions* ». Journal of Statistical Mechanics : Theory and Experiment 2021, n^o 12 (1 décembre 2021) : 124001. http://dx.doi.org/10.1088/1742-5468/ac3908.

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Abstract We consider the problem of learning structures and parameters of continuous-time Bayesian networks (CTBNs) from time-course data under minimal experimental resources. In practice, the cost of generating experimental data poses a bottleneck, especially in the natural and social sciences. A popular approach to overcome this is Bayesian optimal experimental design (BOED). However, BOED becomes infeasible in high-dimensional settings, as it involves integration over all possible experimental outcomes. We propose a novel criterion for experimental design based on a variational approximation of the expected information gain. We show that for CTBNs, a semi-analytical expression for this criterion can be calculated for structure and parameter learning. By doing so, we can replace sampling over experimental outcomes by solving the CTBNs master-equation, for which scalable approximations exist. This alleviates the computational burden of integrating over possible experimental outcomes in high-dimensions. We employ this framework in order to recommend interventional sequences. In this context, we extend the CTBN model to conditional CTBNs in order to incorporate interventions. We demonstrate the performance of our criterion on synthetic and real-world data.

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Xu, J., et C. R. Shelton. « Intrusion Detection using Continuous Time Bayesian Networks ». Journal of Artificial Intelligence Research 39 (23 décembre 2010) : 745–74. http://dx.doi.org/10.1613/jair.3050.

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Intrusion detection systems (IDSs) fall into two high-level categories: network-based systems (NIDS) that monitor network behaviors, and host-based systems (HIDS) that monitor system calls. In this work, we present a general technique for both systems. We use anomaly detection, which identifies patterns not conforming to a historic norm. In both types of systems, the rates of change vary dramatically over time (due to burstiness) and over components (due to service difference). To efficiently model such systems, we use continuous time Bayesian networks (CTBNs) and avoid specifying a fixed update interval common to discrete-time models. We build generative models from the normal training data, and abnormal behaviors are flagged based on their likelihood under this norm. For NIDS, we construct a hierarchical CTBN model for the network packet traces and use Rao-Blackwellized particle filtering to learn the parameters. We illustrate the power of our method through experiments on detecting real worms and identifying hosts on two publicly available network traces, the MAWI dataset and the LBNL dataset. For HIDS, we develop a novel learning method to deal with the finite resolution of system log file time stamps, without losing the benefits of our continuous time model. We demonstrate the method by detecting intrusions in the DARPA 1998 BSM dataset.

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Signorini, Francesca, Martina Panozzi, Agnese Proietti, Greta Alì, Olivia Fanucchi, Alessandro Picchi, Alessandro Ribechini et al. « Conventional Transbronchial Needle Aspiration (cTBNA) and EBUS-Guided Transbronchial Needle Aspiration (EBUS-TBNA) : A Retrospective Study on the Comparison of the Two Methods for Diagnostic Adequacy in Molecular Analysis ». Journal of Molecular Pathology 2, n^o 4 (9 octobre 2021) : 296–305. http://dx.doi.org/10.3390/jmp2040025.

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Introduction: In recent years, there has been a growing development of molecularly targeted therapies for various types of solid tumors—in particular, in non-small-cell lung cancer (NSCLC). This has required the need for greater quantities of tissue that is able to support ancillary studies, alongside cyto-histological diagnoses for the assessment of molecular targets. Conventional TBNA (cTBNA) and EBUS-guided TBNA (EBUS-TBNA) have shown a high diagnostic yield for malignant mediastinal and/or hilar lymph node enlargement and peribronchial masses; however, few studies have compared these two procedures. We retrospectively compared TBNA patients (EBUS-TBNA and cTBNA) in order to determine the diagnostic yield and material adequacy for subsequent ancillary analyses. Materials and Methods: We retrospectively evaluated 318 patients with clinical suspicion of lung cancer or with disease recurrence. All of the patients underwent TBNA (either EBUS-TBNA or cTBNA) on enlarged mediastinal and/or hilar lymph nodes and peribronchial masses between January 2017 and June 2021 at the University Hospital of Pisa, Italy. After a definitive diagnosis, molecular analyses and an evaluation of PD-L1 expression were performed in the cases of adenocarcinoma, squamous cell carcinoma, and NSCLC, not otherwise specified (NOS). Results: EBUS-TBNA was performed in 199 patients and cTBNA was performed in 119 patients with 374 and 142 lymph nodes, respectively. The overall diagnostic yield for positive diagnoses was 59% (diagnostic rate of 61% in EBUS-TBNA, and 55% in cTBNA). Adenocarcinoma (ADC) was the most frequent diagnosis in both methods. EBUS-TBNA diagnostic adequacy was 72% for molecular analysis, while it was 55.5% for cTBNA, showing a statistical trend (p = 0.08) towards the significance of EBUS. The average percentage of neoplastic cells was also statistically different between the two methods (p = 0.05), reaching 51.19 ± 22.14 in EBUS-TBNA and 45.25 ± 22.84 in cTBNA. With regard to the PD-L1 protein expression, the percentage of positivity was similar in both procedures (86% in EBUS-TBNA, 85% in cTBNA). Conclusions: Conventional TBNA (cTBNA) and EBUS-guided TBNA (EBUS-TBNA) are minimally invasive diagnostic methods that are associated with a high diagnostic yield. However, EBUS-TBNA has an improved diagnostic adequacy for molecular analysis compared to cTBNA, and is associated with a higher average percentage of neoplastic cells.

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Song, Xiao Xue, et Shiai Xu. « The Effect of Pre-Crosslinked CTBN on the Mechanical Properties and Morphology of Epoxy Resin ». Advanced Materials Research 1120-1121 (juillet 2015) : 568–71. http://dx.doi.org/10.4028/www.scientific.net/amr.1120-1121.568.

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A novel kind of rubber toughened epoxy was prepared by in situ pre-crosslinking carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN) in the epoxy matrix. The in situ pre-crosslinking of CTBN was initiated by BPO, followed by the curing reaction of epoxy to form the final pre-crosslinked CTBN/epoxy composites. Mechanical properties of epoxy are further improved by the incorporation of pre-crosslinked CTBN compared with its traditional CTBN/epoxy counterparts due to the improved interfacial strength between rubber and epoxy. SEM shows that the size of phase separated rubber particles of pre-crosslinked CTBN/epoxy decreases significantly.

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Li, Guoyou, Yajian Zhou, Jingxian Zhou, Kangfeng Zheng et Yixian Yang. « Finite-SNR Diversity-Multiplexing Tradeoff for Cooperative Transmissions with Opportunistic Network Coding ». Mathematical Problems in Engineering 2012 (2012) : 1–14. http://dx.doi.org/10.1155/2012/437927.

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We present a multiuser cooperative transmission scheme with opportunistic network coding (CTONC), which can improve system performance. In contrast to direct transmission and conventional cooperative transmission, the CTONC allows the relay node to decide whether or not to help do cooperation and employ network coding based on the limited feedback from the destinations. It will not help a transmission pair unless its direct transmission fails. This enables CTONC to make efficient use of the degrees of freedom of the channels. We derive and analyze the diversity-multiplexing tradeoff for the CTONC over Rayleigh fading channels at finite signal-to-noise ratios (SNRs). Theoretical analysis and numerical results show that the proposed scheme achieves better performance gain in terms of average mutual information, outage probability, and finite-SNR diversity-multiplexing tradeoff.

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Xing, Jun, Jayant J. Jayasundar, Yexin Ouyang et Wen-Ji Dong. « Förster Resonance Energy Transfer Structural Kinetic Studies of Cardiac Thin Filament Deactivation ». Journal of Biological Chemistry 284, n^o 24 (15 avril 2009) : 16432–41. http://dx.doi.org/10.1074/jbc.m808075200.

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Cardiac thin filament deactivation is initiated by Ca2+ dissociation from troponin C (cTnC), followed by multiple structural changes of thin filament proteins. These structural transitions are the molecular basis underlying the thin filament regulation of cardiac relaxation, but the detailed mechanism remains elusive. In this study Förster resonance energy transfer (FRET) was used to investigate the dynamics and kinetics of the Ca2+-induced conformational changes of the cardiac thin filaments, specifically the closing of the cTnC N-domain, the cTnC-cTnI (troponin I) interaction, and the cTnI-actin interaction. The cTnC N-domain conformational change was examined by monitoring FRET between a donor (AEDANS) attached to one cysteine residue and an acceptor (DDPM) attached the other cysteine of the mutant cTnC(L13C/N51C). The cTnC-cTnI interaction was investigated by monitoring the distance changes from residue 89 of cTnC to residues 151 and 167 of cTnI, respectively. The cTnI-actin interaction was investigated by monitoring the distance changes from residues 151 and 167 of cTnI to residue 374 of actin. FRET Ca2+ titrations and stopped-flow kinetic measurements show that different thin filament structural transitions have different Ca2+ sensitivities and Ca2+ dissociation-induced kinetics. The observed structural transitions involving the regulatory region and the mobile domain of cTnI occurred at fast kinetic rates, whereas the kinetics of the structural transitions involving the cTnI inhibitory region was slow. Our results suggest that the thin filament deactivation upon Ca2+ dissociation is a two-step process. One step involves rapid binding of the mobile domain of cTnI to actin, which is kinetically coupled with the conformational change of the N-domain of cTnC and the dissociation of the regulatory region of cTnI from cTnC. The other step involves switching the inhibitory region of cTnI from interacting with cTnC to interacting with actin. The latter processes may play a key role in regulating cross-bridge kinetics.

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Korte, F. Steven, Erik R. Feest, Maria V. Razumova, An-Yue Tu et Michael Regnier. « Enhanced Ca2+ binding of cardiac troponin reduces sarcomere length dependence of contractile activation independently of strong crossbridges ». American Journal of Physiology-Heart and Circulatory Physiology 303, n^o 7 (1 octobre 2012) : H863—H870. http://dx.doi.org/10.1152/ajpheart.00395.2012.

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Calcium sensitivity of the force-pCa relationship depends strongly on sarcomere length (SL) in cardiac muscle and is considered to be the cellular basis of the Frank-Starling law of the heart. SL dependence may involve changes in myofilament lattice spacing and/or myosin crossbridge orientation to increase probability of binding to actin at longer SLs. We used the L48Q cardiac troponin C (cTnC) variant, which has enhanced Ca2+ binding affinity, to test the hypotheses that the intrinsic properties of cTnC are important in determining 1) thin filament binding site availability and responsiveness to crossbridge activation and 2) SL dependence of force in cardiac muscle. Trabeculae containing L48Q cTnC-cTn lost SL dependence of the Ca2+ sensitivity of force. This occurred despite maintaining the typical SL-dependent changes in maximal force (Fmax). Osmotic compression of preparations at SL 2.0 μm with 3% dextran increased Fmax but not pCa50 in L48Q cTnC-cTn exchanged trabeculae, whereas wild-type (WT)-cTnC-cTn exchanged trabeculae exhibited increases in both Fmax and pCa50. Furthermore, crossbridge inhibition with 2,3-butanedione monoxime at SL 2.3 μm decreased Fmax and pCa50 in WT cTnC-cTn trabeculae to levels measured at SL 2.0 μm, whereas only Fmax was decreased with L48Q cTnC-cTn. Overall, these results suggest that L48Q cTnC confers reduced crossbridge dependence of thin filament activation in cardiac muscle and that changes in the Ca2+ sensitivity of force in response to changes in SL are at least partially dependent on properties of thin filament troponin.

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Liu, Lizhu, Hong Zhang, Nan Zhang et Ling Weng. « The preparation and application of CTBN modified epoxy adhesive ». Pigment & ; Resin Technology 44, n^o 6 (2 novembre 2015) : 358–63. http://dx.doi.org/10.1108/prt-10-2014-0099.

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Purpose – The purpose of this study is to investigate the effects of two epoxy ratio and carboxyl-terminated butadiene solid rubber (CTBN) content on adhesive and flexible copper clad laminate (FCCL) performance. The epoxy adhesive used for FCCL was prepared with epoxy resin of 901 and 6128 as matrix and CTBN as toughener. Design/methodology/approach – The epoxy adhesive was prepared with epoxy resin as matrix, CTBN as toughener and 4,4′-diamino diphenyl sulfone as curing agent in solvent of butanone by mechanical agitation. The adhesives were cast on the polyimide film; subsequently, the polyimide film was dried at 160°C for 3 min to remove the solvent. Then, it was laminated with copper foil at 180°C with the pressure of 12 MPa for 3 min. The FCCL was obtained after heating for 3 h in a vacuum oven at 160°C. The structure and dielectric properties of cured adhesive, surface morphology of peeling FCCL and mechanical properties of FCCL were determined. Findings – CTBN was found to react with the epoxy resin during the curing process, with the rubber phase being precipitated and dispersed in the epoxy matrix. The relative dielectric constant and the dielectric loss tangent slightly increased with increasing CTBN content. The peeling strength of FCCL increased accompanied by a decrease of folding resistance with the increase of 901 content. Further, with the addition of XNBR, the peel strength of FCCL increased, as well as the folding resistance of FCCL, but at a higher XNBR level of 20 weight per cent, the folding resistance of FCCL tended to decrease. Research limitations/implications – In the study reported here, the effects of different epoxy resin molecular weight and CTBN content were investigated. Results of this research could benefit in-depth understanding of the influence of epoxy resin molecular weight and CTBN content on adhesive performance and could further promote the development of epoxy adhesive. Practical implications – The adhesion of epoxy adhesive prepared from epoxy resin with different molecular weight and CTBN increased, leading to the increase in peeling strength and folding resistance of FCCL. Social implications – The peeling strength of FCCL increased as the adhesion strength of epoxy adhesive increased by adding CTBN, making FCCL widely applicable. Originality/value – The mechanical properties of epoxy adhesive were increased by adding CTBN. The effects of CTBN on the microstructure and properties of FCCL were discussed in detail.

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Bian, Xingming, Rui Tuo, Wei Yang, Yiran Zhang, Qing Xie, Junwei Zha, Jun Lin et Shaojian He. « Mechanical, Thermal, and Electrical Properties of BN–Epoxy Composites Modified with Carboxyl-Terminated Butadiene Nitrile Liquid Rubber ». Polymers 11, n^o 10 (23 septembre 2019) : 1548. http://dx.doi.org/10.3390/polym11101548.

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Filled high thermal conductivity epoxy composite solves the problem of the low thermal conductivity of the epoxy resin itself, but the addition of the thermal conductive filler reduces the mechanical properties of the composite, which limits its application in the field of high voltage insulation. In this work, carboxyl-terminated butadiene nitrile liquid rubber (CTBN) was used to toughen the boron nitride-epoxy hybrid system, and the effects of different contents of CTBN on the mechanical properties, thermal conductivity, glass transition temperature, thermal stability, and dielectric properties of the composites were investigated. The results showed that when the content of CTBN was 5–15 wt.%, the CTBN formed a dispersed island structure in the epoxy resin matrix. The toughness of the composite increased by about 32%, the breakdown strength was improved, and the thermal conductivity was about 160% higher than that of pure epoxy resin. As the CTBN content increased, the glass transition temperature and thermal stability of the composite decreased and the dielectric constant and the dielectric loss increased. When the CTBN content is 10–15 wt.%, a toughened epoxy composite material with better comprehensive properties is obtained.

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Ouyang, Chun Fa, Qun Gao, Yu Tao Shi et Wen Tao Li. « Effect of CTBN on Properties of Oxide Graphene/Epoxy Resin Composites ». Advanced Materials Research 412 (novembre 2011) : 393–96. http://dx.doi.org/10.4028/www.scientific.net/amr.412.393.

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The effect of liquid carboxyl terminated butadiene acrylonitrile copolymer (CTBN) on the properties of oxide graphene (OG) /epoxy resin (EP) composite has been studied. The results show that oscillations process can greatly increase the tensile strength, shear strength and hardness of the composites, for the compatibility between the EP and the OG can be greatly improved after oscillations. Infra-red analysis shows that CTBN reacts with EP to form ester group. The tensile strength of the EP decrease, and the elongation at break increase, as more and more CTBN added. The tensile strength of the OG/EP composite is 14.37 MPa, while that of CTBN/OG/EP (15/0.001/100) composite is 4.84 MPa.

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Yan, Chunhong, et John S. Sack. « X-ray structure of a human cardiac muscle troponin C/troponin I chimera in two crystal forms ». Acta Crystallographica Section F Structural Biology Communications 78, n^o 1 (1 janvier 2022) : 17–24. http://dx.doi.org/10.1107/s2053230x21012395.

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The X-ray crystal structure of a human cardiac muscle troponin C/troponin I chimera has been determined in two different crystal forms and shows a conformation of the complex that differs from that previously observed by NMR. The chimera consists of the N-terminal domain of troponin C (cTnC; residues 1–80) fused to the switch region of troponin I (cTnI; residues 138–162). In both crystal forms, the cTnI residues form a six-turn α-helix that lays across the hydrophobic groove of an adjacent cTnC molecule in the crystal structure. In contrast to previous models, the cTnI helix runs in a parallel direction relative to the cTnC groove and completely blocks the calcium desensitizer binding site of the cTnC–cTnI interface.

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Cid, Gabriela C., Mariana P. B. Jardim, Amanda C. Jesus, Samay Z. R. Costa, Ilka N. Gonçalves, Tiago C. Peixoto, Heloisa J. M. Souza et Vivian A. Nogueira. « Clinical-pathological and immunohistochemical evaluations of cardiac lesions in cats with chronic kidney disease ». Pesquisa Veterinária Brasileira 40, n^o 12 (décembre 2020) : 1002–9. http://dx.doi.org/10.1590/1678-5150-pvb-6739.

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ABSTRACT: Chronic kidney disease (CKD) is characterized by irreversible morphostructural lesions that can progressively evolve to chronic renal insufficiency and kidney failure. It is known that the heart and kidneys are closely related, and that communication between these organs occurs through a variety of pathways; subtle physiological changes in one of them are compensated by the other. Histopathological cardiac evaluation through routine staining presents a limitation to identify specific or discreet lesions in the cardiomyocytes. This study aimed to evaluate serum troponin levels in cats with CKD, associated with clinical and pathological findings, as well as to correlate the morphostructural cardiac lesions to determine their distribution through macroscopic and histological assessments and anti-cardiac troponin C (cTnC) immunohistochemistry (IHC). To this end, 20 cats (18 diagnosed with CKD and two controls) were selected. Anti-human cTnC IHC was conducted after necropsy and separation in eight regions of each collected heart. Heart fragments from two cats without CKD were used as controls. The anti-human cTnC antibody is useful in detecting cardiac lesions and has shown decreased expression in cardiomyocytes of cats with CKD. Serum troponin was above the reference values in 11/18 (61.11%) animals and decreased expression for the cTnC antibody was observed in individual cardiomyocytes in 9/18 (50%) animals. It was verified that the number of regions with decreased expression for the cTnC antibody in cardiomyocytes is significantly correlated with serum troponin. The anti-human cTnC antibody has been found effective in detecting cardiac lesions and has shown decreased expression in the cardiomyocytes of cats with CKD. Correlation was observed between increased serum cTnI and loss of immunoreactivity at anti-cTnC antibody IHC in cats with CKD, which proves damage to cardiomyocytes secondary to kidney disease.

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Parmacek, M. S., A. J. Vora, T. Shen, E. Barr, F. Jung et J. M. Leiden. « Identification and characterization of a cardiac-specific transcriptional regulatory element in the slow/cardiac troponin C gene ». Molecular and Cellular Biology 12, n^o 5 (mai 1992) : 1967–76. http://dx.doi.org/10.1128/mcb.12.5.1967-1976.1992.

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The slow/cardiac troponin C (cTnC) gene has been used as a model system for defining the molecular mechanisms that regulate cardiac and skeletal muscle-specific gene expression during mammalian development. cTnC is expressed continuously in both embryonic and adult cardiac myocytes but is expressed only transiently in embryonic fast skeletal myotubes. We have reported previously that cTnC gene expression in skeletal myotubes is controlled by a developmentally regulated, skeletal muscle-specific transcriptional enhancer located within the first intron of the gene (bp 997 to 1141). In this report, we show that cTnC gene expression in cardiac myocytes both in vitro and in vivo is regulated by a distinct and independent transcriptional promoter and enhancer located within the immediate 5' flanking region of the gene (bp -124 to +32). DNase I footprint and electrophoretic mobility shift assay analyses demonstrated that this cardiac-specific promoter/enhancer contains five nuclear protein binding sites (designated CEF1, CEF-2, and CPF1-3), four of which bind novel cardiac-specific nuclear protein complexes. Functional analysis of the cardiac-specific cTnC enhancer revealed that mutation of either the CEF-1 or CEF-2 nuclear protein binding site abolished the activity of the cTnC enhancer in cardiac myocytes. Taken together, these results define a novel mechanism for developmentally regulating a single gene in multiple muscle cell lineages. In addition, they identify previously undefined cardiac-specific transcriptional regulatory motifs and trans-acting factors. Finally, they demonstrate distinct transcriptional regulatory pathways in cardiac and skeletal muscle.

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Parmacek, M. S., A. J. Vora, T. Shen, E. Barr, F. Jung et J. M. Leiden. « Identification and characterization of a cardiac-specific transcriptional regulatory element in the slow/cardiac troponin C gene. » Molecular and Cellular Biology 12, n^o 5 (mai 1992) : 1967–76. http://dx.doi.org/10.1128/mcb.12.5.1967.

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The slow/cardiac troponin C (cTnC) gene has been used as a model system for defining the molecular mechanisms that regulate cardiac and skeletal muscle-specific gene expression during mammalian development. cTnC is expressed continuously in both embryonic and adult cardiac myocytes but is expressed only transiently in embryonic fast skeletal myotubes. We have reported previously that cTnC gene expression in skeletal myotubes is controlled by a developmentally regulated, skeletal muscle-specific transcriptional enhancer located within the first intron of the gene (bp 997 to 1141). In this report, we show that cTnC gene expression in cardiac myocytes both in vitro and in vivo is regulated by a distinct and independent transcriptional promoter and enhancer located within the immediate 5' flanking region of the gene (bp -124 to +32). DNase I footprint and electrophoretic mobility shift assay analyses demonstrated that this cardiac-specific promoter/enhancer contains five nuclear protein binding sites (designated CEF1, CEF-2, and CPF1-3), four of which bind novel cardiac-specific nuclear protein complexes. Functional analysis of the cardiac-specific cTnC enhancer revealed that mutation of either the CEF-1 or CEF-2 nuclear protein binding site abolished the activity of the cTnC enhancer in cardiac myocytes. Taken together, these results define a novel mechanism for developmentally regulating a single gene in multiple muscle cell lineages. In addition, they identify previously undefined cardiac-specific transcriptional regulatory motifs and trans-acting factors. Finally, they demonstrate distinct transcriptional regulatory pathways in cardiac and skeletal muscle.

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Genge, Christine E., William S. Davidson et Glen F. Tibbits. « Adult teleost heart expresses two distinct troponin C paralogs : cardiac TnC and a novel and teleost-specific ssTnC in a chamber- and temperature-dependent manner ». Physiological Genomics 45, n^o 18 (15 septembre 2013) : 866–75. http://dx.doi.org/10.1152/physiolgenomics.00074.2013.

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The teleost-specific whole genome duplication created multiple copies of genes allowing for subfunctionalization of isoforms. In this study, we show that the teleost cardiac Ca2+-binding troponin C (TnC) is the product of two distinct genes: cardiac TnC (cTnC, TnnC1a) and a fish-specific slow skeletal TnC (ssTnC, TnnC1b). The ssTnC gene is novel to teleosts as mammals have a single gene commonly referred as cTnC but which is also expressed in slow skeletal muscle. In teleosts, the data strongly indicate that these are two TnC genes are different paralogs. Because we determined that ssTnC exists across many teleosts but not in basal ray-finned fish (e.g., bichir), we propose that these paralogs are the result of an ancestral tandem gene duplication persisting only in teleosts. Quantification of mRNA levels was used to demonstrate distinct expression localization patterns of the paralogs within the chambers of the heart. In the adult zebrafish acclimated at 28°C, ssTnC mRNA levels are twofold greater than cTnC mRNA levels in the atrium, whereas cTnC mRNA was almost exclusively expressed in the ventricle. Meanwhile, rainbow trout acclimated at 5°C showed cTnC mRNA levels in both chambers significantly greater than ssTnC. Distinct responses to temperature acclimation were also quantified in both adult zebrafish and rainbow trout, with mRNA in both chambers shifting to express higher levels of cTnC in 18°C acclimated zebrafish and 5°C acclimated trout. Possible subfunctionalization of TnC isoforms may provide insight into how teleosts achieve physiological versatility in chamber-specific contractile properties.

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Zarrella, Giuliana, Mitchell Lavoie, Melissa Gardner, Patrick Johnson, Areej El-Jawahri et Michael Parsons. « NCOG-48. A PROSPECTIVE LONGITUDINAL NEUROCOGNITIVE OUTCOME STUDY IN PATIENTS TREATED WITH CAR-T-CELL THERAPY AT 6 MONTHS ». Neuro-Oncology 24, Supplement_7 (1 novembre 2022) : vii208. http://dx.doi.org/10.1093/neuonc/noac209.799.

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Abstract INTRODUCTION Chimeric Antigen Receptor T-cell (CAR-T) therapy carries risk of significant neurocognitive function (NCF) toxicities. Longer term NCF outcomes have yet to be reported. The goal of the current study was to assess NCF prospectively in patients undergoing CAR-T. METHODS Adult patients undergoing CAR-T participated in NCF testing with a cognitive clinical trial battery (CTB) at baseline and 6 months after treatment. Group change on each test and on the composite score (CTBC) was examined with paired t-tests and individual change, defined as +/-1 SD on CTBC, was also reported. RESULTS Forty patients (Mage=62.45, 63% male, 97% Non-Hispanic or Latino) completed NCF testing at baseline, and 28 patients completed NCF measures 6 months post-CAR-T (20 complete CTBC, 8 partial CTB, completed virtually). At baseline, 13/40 patients (33%) had significant impairment in NCF (CTBC Z-score < -1.5), and 2/20 (10%) were impaired at follow-up. In the 20 individuals with pre- and 6-month post-CAR-T CTBC scores, there was no significant change (t(19)=-0.926; p=0.366). Examination of each individual test score also showed no changes (immediate memory (t(26)=-0.084; p=0.934), delayed memory (t(26)=-0.207; p=0.837), memory recognition (t (26)=-0.062; p=0.951) executive function (t(18)=-0.447, p=0.660), and verbal fluency (t(27)=-0.035, p=0.972)). Individual analyses of CTBC at follow-up found the number of patients with meaningful decline=1 (5%), improvement=2 (10%), and no change=17 (85%) on CTBC. CONCLUSION Although CAR-T can be associated with acute change in NCF, this prospective longitudinal study showed stable cognitive performance 6 months after treatment. To our knowledge, this is the longest prospective longitudinal study of NCF in CAR-T survivors. This study is limited in that some subjects completed NCF testing virtually at follow-up, limiting the sample size for unconfounded comparison of performance. Future work will examine longer term outcomes and subjective cognitive function in CAR-T survivors.

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Pavarini, Saulo Petinatti, Marcele Bettim Bandinelli, Gregory Duarte Juffo, Suyene Oltramari de Souza, David Driemeier et Cláudio Estêvão Farias da Cruz. « Decreased expression of cardiac troponin C is associated with cardiac lesions in Amorimia exotropica poisoned cattle ». Pesquisa Veterinária Brasileira 32, n^o 10 (octobre 2012) : 1005–8. http://dx.doi.org/10.1590/s0100-736x2012001000010.

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The plants which cause sudden death of cattle in Brazil occupy a leading position for losses in the cattle industry. Amorimia exotropica is one of the plants pertaining to this group. Diagnostic findings in these cases may be inconclusive; further knowledge is necessary. This paper identifies cardiac lesions through anti-cardiac troponin C (cTnC) immunehistochemistry performed in tissues from cattle poisoned after consumption of A.exotropica in southern Brazil. Heart fragments from nine A. exotropica-poisoned cattle were studied immunohistochemically using anti-human cTnC as the primary antibody. In the hearts from all of the poisoned cattle, there was a sharp decrease in the cTnC expression level in the cytoplasm of groups of cardiomyocytes. A significant decrease in anti-cTnC immunoreactivity occurred particularly in degenerated or necrotic cardiomyocytes. Occasional groups of cells showed complete loss of immunolabeling. In the remaining intact cardiomyocytes from poisoned cattle and in cardiomyocytes from six cattle that died from other causes there was intense cytoplasmic staining.

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Gillis, Todd E., Chris D. Moyes et Glen F. Tibbits. « Sequence mutations in teleost cardiac troponin C that are permissive of high Ca2+ affinity of site II ». American Journal of Physiology-Cell Physiology 284, n^o 5 (1 mai 2003) : C1176—C1184. http://dx.doi.org/10.1152/ajpcell.00339.2002.

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Cardiac myofibrils isolated from trout heart have been demonstrated to have a higher sensitivity for Ca2+ than mammalian cardiac myofibrils. Using cardiac troponin C (cTnC) cloned from trout and mammalian hearts, we have previously demonstrated that this comparatively high Ca2+ sensitivity is due, in part, to trout cTnC (ScTnC) having twice the Ca2+ affinity of mammalian cTnC (McTnC) over a broad range of temperatures. The amino acid sequence of ScTnC is 92% identical to McTnC. To determine the residues responsible for the high Ca2+ affinity, the function of a number of ScTnC and McTnC mutants was characterized by monitoring an intrinsic fluorescent reporter that monitors Ca2+ binding to site II (F27W). The removal of the COOH terminus (amino acids 90–161) from ScTnC and McTnC maintained the difference in Ca2+ affinity between the truncated cTnC isoforms (ScNTnC and McNTnC). The replacement of Gln29 and Asp30 in ScNTnC with the corresponding residues from McNTnC, Leu and Gly, respectively, reduced Ca2+ affinity to that of McNTnC. These results demonstrate that Gln29 and Asp30 in ScTnC are required for the high Ca2+ affinity of site II.

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Ko, Joseph, Trevor Krasowsky et George Ban-Weiss. « Measurements to determine the mixing state of black carbon emitted from the 2017–2018 California wildfires and urban Los Angeles ». Atmospheric Chemistry and Physics 20, n^o 24 (17 décembre 2020) : 15635–64. http://dx.doi.org/10.5194/acp-20-15635-2020.

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Abstract. The effects of atmospheric black carbon (BC) on climate and public health have been well established, but large uncertainties remain regarding the extent of the impacts of BC at different temporal and spatial scales. These uncertainties are largely due to the heterogeneous nature of BC in terms of its spatiotemporal distribution, mixing state, and coating composition. Here, we seek to further understand the size and mixing state of BC emitted from various sources and aged over different timescales using field measurements in the Los Angeles region. We measured refractory black carbon (rBC) with a single-particle soot photometer (SP2) on Catalina Island, California (∼70 km southwest of downtown Los Angeles) during three different time periods. During the first campaign (September 2017), westerly winds were dominant and measured air masses were representative of well-aged background over the Pacific Ocean. In the second and third campaigns (December 2017 and November 2018, respectively), atypical Santa Ana wind conditions allowed us to measure biomass burning rBC (BCbb) from air masses dominated by large biomass burning events in California and fossil fuel rBC (BCff) from the Los Angeles Basin. We observed that the emissions source type heavily influenced both the size distribution of the rBC cores and the rBC mixing state. BCbb had thicker coatings and larger core diameters than BBff. We observed a mean coating thickness (CTBC) of ∼40–70 nm and a count mean diameter (CMD) of ∼120 nm for BCbb. For BCff, we observed a CTBC of ∼5–15 nm and a CMD of ∼100 nm. Our observations also provided evidence that aging led to an increased CTBC for both BCbb and BCff. Aging timescales < ∼1 d were insufficient to thickly coat freshly emitted BCff. However, CTBC for aged BCff within aged background plumes was ∼35 nm thicker than CTBC for fresh BCff. Likewise, we found that CTBC for aged BCbb was ∼18 nm thicker than CTBC for fresh BCbb. The results presented in this study highlight the wide variability in the BC mixing state and provide additional evidence that the emissions source type and aging influence rBC microphysical properties.

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Yadav, Ranjana, et Deepak Srivastava. « Studies on cardanol-based epoxidized novolac resin and its blends ». Chemistry & ; Chemical Technology 2, n^o 3 (15 septembre 2008) : 173–84. http://dx.doi.org/10.23939/chcht02.03.173.

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Cardanol-based novolac-type phenolic resin was synthesized with a mole ratio 1.0:0.5 of cardanol-to-formaldehyde using a dicarboxylic acid catalyst such as succinic acid. The cardanol-based novolac-type phenolic resin may further be modified by epoxidation with epichlorohydrin excess at 393 K in a basic medium to duplicate the performance of such phenolic-type novolacs. Carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) has been studied by various researches with diglycidyl ether of bisphenol-A (DEGBA) epoxy resin and epoxidized phenolic novolac resins. The epoxidized novolac resin was blended with different weight ratios of carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) and cured with a stoichiometric amount of polyamine curing agent. The formation of various products during the synthesis of cardanol-based novolac resin, epoxodized novolac resin and blending of epoxidized novolac resin with CTBN has been studied by Fourier-transform infrared (FTIR) spectroscopic analysis. Further, the products were confirmed by a proton nuclear magnetic resonance (1H-NMR) spectroscopic analysis. The number average molecular weight was determined by a gel permeation chromatography (GPC) analysis. The blend sample, having 15 wt % CTBN concentration showed minimum cure time and most thermally stable systems.

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Tikunova, Svetlana B., Andres Cuesta, Morgan Price, Monica X. Li, Natalya Belevych, Brandon J. Biesiadecki, Peter J. Reiser, Peter M. Hwang et Jonathan P. Davis. « 3-Chlorodiphenylamine activates cardiac troponin by a mechanism distinct from bepridil or TFP ». Journal of General Physiology 151, n^o 1 (15 novembre 2018) : 9–17. http://dx.doi.org/10.1085/jgp.201812131.

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Despite extensive efforts spanning multiple decades, the development of highly effective Ca2+ sensitizers for the heart remains an elusive goal. Existing Ca2+ sensitizers have other targets in addition to cardiac troponin (cTn), which can lead to adverse side effects, such as hypotension or arrhythmias. Thus, there is a need to design Ca2+-sensitizing drugs with higher affinity and selectivity for cTn. Previously, we determined that many compounds based on diphenylamine (DPA) were able to bind to a cTnC–cTnI chimera with moderate affinity (Kd ∼10–120 µM). Of these compounds, 3-chlorodiphenylamine (3-Cl-DPA) bound most tightly (Kd of 10 µM). Here, we investigate 3-Cl-DPA further and find that it increases the Ca2+ sensitivity of force development in skinned cardiac muscle. Using NMR, we show that, like the known Ca2+ sensitizers, trifluoperazine (TFP) and bepridil, 3-Cl-DPA is able to bind to the isolated N-terminal domain (N-domain) of cTnC (Kd of 6 µM). However, while the bulky molecules of TFP and bepridil stabilize the open state of the N-domain of cTnC, the small and flexible 3-Cl-DPA molecule is able to bind without stabilizing this open state. Thus, unlike TFP, which drastically slows the rate of Ca2+ dissociation from the N-domain of isolated cTnC in a dose-dependent manner, 3-Cl-DPA has no effect on the rate of Ca2+ dissociation. On the other hand, the affinity of 3-Cl-DPA for a cTnC–TnI chimera is at least an order of magnitude higher than that of TFP or bepridil, likely because 3-Cl-DPA is less disruptive of cTnI binding to cTnC. Therefore, 3-Cl-DPA has a bigger effect on the rate of Ca2+ dissociation from the entire cTn complex than TFP and bepridil. Our data suggest that 3-Cl-DPA activates the cTn complex via a unique mechanism and could be a suitable scaffold for the development of novel treatments for systolic heart failure.

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Coşğun, İbrahim Güven, Ersin Günay, Şule Çilekar et Sibel Günay. « Efficacy of TBNA needles for EBUS during fiberoptic bronchoscopy ? » Health Sciences Quarterly 2, n^o 3 (28 juillet 2022) : 149–55. http://dx.doi.org/10.26900/hsq.2.3.04.

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Conventional transbronchial needle aspiration (cTBNA) biopsy is a diagnostic minimally invasive technique applied using fibreoptic bronchoscopy (FOB) in the evaluation of mediastinal/hilar lymph nodes. With the development of endobronchial ultrasound (EBUS) devices, transbronchial aspiration needles have been revised for use according to the EBUS guidelines. The main aim of this research was to evaluate the diagnostic success of transbronchial aspiration needles that was produced for EBUS when it was applied with FOB instead of conventional TBNA. A retrospective examination was made with the data of 35 patients applied with FOB TBNA, using needles specifically designed for EBUS and 36 patients with conventional TBNA (cTBNA group), for lung cancer staging or the diagnosis of mediastinal lymphadenopathy between November 2018 and November 2019. Seventy-two and sixty procedures performed on 71 patients were included in the study. Diagnostic efficiency for TBNA and cTBNA groups were 91.4% and 83.3%, respectively. Conventional TBNA is still acceptable when the low cost and ease of application are taken into consideration. In conclusion, improvement of current conventional TBNA needles similar to EBUS-TBNA needles for more efficient aspiration capacity could be the first stepto increasing the TBNA diagnostic yield. Nevertheless, further studies are needed to confirm our results.

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Ip, H. S., D. B. Wilson, M. Heikinheimo, Z. Tang, C. N. Ting, M. C. Simon, J. M. Leiden et M. S. Parmacek. « The GATA-4 transcription factor transactivates the cardiac muscle-specific troponin C promoter-enhancer in nonmuscle cells ». Molecular and Cellular Biology 14, n^o 11 (novembre 1994) : 7517–26. http://dx.doi.org/10.1128/mcb.14.11.7517-7526.1994.

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The unique contractile phenotype of cardiac myocytes is determined by the expression of a set of cardiac muscle-specific genes. By analogy to other mammalian developmental systems, it is likely that the coordinate expression of cardiac genes is controlled by lineage-specific transcription factors that interact with promoter and enhancer elements in the transcriptional regulatory regions of these genes. Although previous reports have identified several cardiac muscle-specific transcriptional elements, relatively little is known about the lineage-specific transcription factors that regulate these elements. In this report, we demonstrate that the slow/cardiac muscle-specific troponin C (cTnC) enhancer contains a specific binding site for the lineage-restricted zinc finger transcription factor GATA-4. This GATA-4-binding site is required for enhancer activity in primary cardiac myocytes. Moreover, the cTnC enhancer can be transactivated by overexpression of GATA-4 in non-cardiac muscle cells such as NIH 3T3 cells. In situ hybridization studies demonstrate that GATA-4 and cTnC have overlapping patterns of expression in the hearts of postimplantation mouse embryos and that GATA-4 gene expression precedes cTnC expression. Indirect immunofluorescence reveals GATA-4 expression in cultured cardiac myocytes from neonatal rats. Taken together, these results are consistent with a model in which GATA-4 functions to direct tissue-specific gene expression during mammalian cardiac development.

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Ip, H. S., D. B. Wilson, M. Heikinheimo, Z. Tang, C. N. Ting, M. C. Simon, J. M. Leiden et M. S. Parmacek. « The GATA-4 transcription factor transactivates the cardiac muscle-specific troponin C promoter-enhancer in nonmuscle cells. » Molecular and Cellular Biology 14, n^o 11 (novembre 1994) : 7517–26. http://dx.doi.org/10.1128/mcb.14.11.7517.

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The unique contractile phenotype of cardiac myocytes is determined by the expression of a set of cardiac muscle-specific genes. By analogy to other mammalian developmental systems, it is likely that the coordinate expression of cardiac genes is controlled by lineage-specific transcription factors that interact with promoter and enhancer elements in the transcriptional regulatory regions of these genes. Although previous reports have identified several cardiac muscle-specific transcriptional elements, relatively little is known about the lineage-specific transcription factors that regulate these elements. In this report, we demonstrate that the slow/cardiac muscle-specific troponin C (cTnC) enhancer contains a specific binding site for the lineage-restricted zinc finger transcription factor GATA-4. This GATA-4-binding site is required for enhancer activity in primary cardiac myocytes. Moreover, the cTnC enhancer can be transactivated by overexpression of GATA-4 in non-cardiac muscle cells such as NIH 3T3 cells. In situ hybridization studies demonstrate that GATA-4 and cTnC have overlapping patterns of expression in the hearts of postimplantation mouse embryos and that GATA-4 gene expression precedes cTnC expression. Indirect immunofluorescence reveals GATA-4 expression in cultured cardiac myocytes from neonatal rats. Taken together, these results are consistent with a model in which GATA-4 functions to direct tissue-specific gene expression during mammalian cardiac development.

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McCubbin, William D., et Cyril M. Kay. « Trypsin digestion of bovine cardiac troponin C in the presence and absence of calcium ». Canadian Journal of Biochemistry and Cell Biology 63, n^o 8 (1 août 1985) : 812–23. http://dx.doi.org/10.1139/o85-103.

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The rate of tryptic digestion of cardiac troponin C (cTNC) has been shown to be dependent on Ca2+ as was noted earlier for skeletal TNC (sTNC). Two representative peptides have been characterized on the basis of amino acid composition and partial amino terminal sequence analysis. Circular dichroism and fluorescence studies monitored their response to the presence of Ca2+. Their ability to form complexes with the ATPase inhibitory subunit of cardiac troponin (cTNI) was determined by urea –polyacrylamide gel electrophoresis and fluorescence experiments. The ability of these peptides to substitute for whole cTNC in restoring the ATPase activity of a partially inhibited synthetic actomyosin system was also explored. The N-terminal peptide 1–88 already contains a large amount of ordered structure, which indicates that the α-helices flanking binding site II of cTNC exist independently of Ca2+. Consequently this peptide shows limited increase in structure in the presence of Ca2+. It binds to cTNI independently of the presence of Ca2+ and could substitute for whole cTNC by relaxing the inhibitory effect of cTNI. The C-terminal peptide 103–158 has a low amount of secondary structure in the absence of Ca2+ but this increases dramatically in the presence of this cation. This peptide could only form a stable complex with cTNI in the presence of Ca2+ and was unable to release the inhibitory effect of cTNI.

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Vineeta, Nigam, D. K. Setua et G. N. Mathur. « Chemical Interaction and Phase Morphology Development of Carboxy Terminated Butadiene-co-Acrylonitrile Rubber Toughened Epoxy Blends ». Rubber Chemistry and Technology 73, n^o 5 (1 novembre 2000) : 830–38. http://dx.doi.org/10.5254/1.3547622.

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Abstract The nature of chemical interaction between carboxy terminated butadiene-co-acrylonitrile (CTBN), a reactive liquid rubber, and epoxy cresol novolac (ECN) resin during curing with diamino diphenyl methane (DDM) as hardener has been studied by Fourier transform infrared spectroscopy (FTIR). Blends of CTBN and ECN were withdrawn at a regular interval of 15 min for 2 h and the FTIR spectra were recorded in each case. Variations of the positions of the characteristic peaks of the oxirane group of epoxy and carboxyl group of CTBN as well as formation of several new peaks with the progress of the curing were observed. Scanning electron microscopy (SEM) was conducted in each of the above samples to study the evolution of phase morphology through growth of the rubber phase while the continuous epoxy matrix underwent curing by the hardener. The surface topography and microstructure of impact-failed toughened epoxies have also been studied with the help of atomic force microscopy (AFM).

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Parmacek, M. S., H. S. Ip, F. Jung, T. Shen, J. F. Martin, A. J. Vora, E. N. Olson et J. M. Leiden. « A novel myogenic regulatory circuit controls slow/cardiac troponin C gene transcription in skeletal muscle ». Molecular and Cellular Biology 14, n^o 3 (mars 1994) : 1870–85. http://dx.doi.org/10.1128/mcb.14.3.1870-1885.1994.

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The slow/cardiac troponin C (cTnC) gene is expressed in three distinct striated muscle lineages: cardiac myocytes, embryonic fast skeletal myotubes, and adult slow skeletal myocytes. We have reported previously that cTnC gene expression in cardiac muscle is regulated by a cardiac-specific promoter/enhancer located in the 5' flanking region of the gene (bp -124 to +1). In this report, we demonstrate that the cTnC gene contains a second distinct and independent transcriptional enhancer which is located in the first intron. This second enhancer is skeletal myotube specific and is developmentally up-regulated during the differentiation of myoblasts to myotubes. This enhancer contains three functionally important nuclear protein binding sites: a CACCC box, a MEF-2 binding site, and a previously undescribed nuclear protein binding site, designated MEF-3, which is also present in a large number of skeletal muscle-specific transcriptional enhancers. Unlike most skeletal muscle-specific transcriptional regulatory elements, the cTnC enhancer does not contain a consensus binding site (CANNTG) for the basic helix-loop-helix (bHLH) family of transcription factors and does not directly bind MyoD-E12 protein complexes. Despite these findings, the cTnC enhancer can be transactivated by overexpression of the myogenic bHLH proteins, MyoD and myogenin, in C3H10T1/2 (10T1/2) cells. Electrophoretic mobility shift assays demonstrated changes in the patterns of MEF-2, CACCC, and MEF-3 DNA binding activities following the conversion of 10T1/2 cells into myoblasts and myotubes by stable transfection with a MyoD expression vector. In particular, MEF-2 binding activity was up-regulated in 10T1/2 cells stably transfected with a MyoD expression vector only after these cells fused and differentiated into skeletal myotubes. Taken together, these results demonstrated that distinct lineage-specific transcriptional regulatory elements control the expression of a single myofibrillar protein gene in fast skeletal and cardiac muscle. In addition, they show that bHLH transcription factors can indirectly transactivate the expression of some muscle-specific genes.

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Parmacek, M. S., H. S. Ip, F. Jung, T. Shen, J. F. Martin, A. J. Vora, E. N. Olson et J. M. Leiden. « A novel myogenic regulatory circuit controls slow/cardiac troponin C gene transcription in skeletal muscle. » Molecular and Cellular Biology 14, n^o 3 (mars 1994) : 1870–85. http://dx.doi.org/10.1128/mcb.14.3.1870.

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The slow/cardiac troponin C (cTnC) gene is expressed in three distinct striated muscle lineages: cardiac myocytes, embryonic fast skeletal myotubes, and adult slow skeletal myocytes. We have reported previously that cTnC gene expression in cardiac muscle is regulated by a cardiac-specific promoter/enhancer located in the 5' flanking region of the gene (bp -124 to +1). In this report, we demonstrate that the cTnC gene contains a second distinct and independent transcriptional enhancer which is located in the first intron. This second enhancer is skeletal myotube specific and is developmentally up-regulated during the differentiation of myoblasts to myotubes. This enhancer contains three functionally important nuclear protein binding sites: a CACCC box, a MEF-2 binding site, and a previously undescribed nuclear protein binding site, designated MEF-3, which is also present in a large number of skeletal muscle-specific transcriptional enhancers. Unlike most skeletal muscle-specific transcriptional regulatory elements, the cTnC enhancer does not contain a consensus binding site (CANNTG) for the basic helix-loop-helix (bHLH) family of transcription factors and does not directly bind MyoD-E12 protein complexes. Despite these findings, the cTnC enhancer can be transactivated by overexpression of the myogenic bHLH proteins, MyoD and myogenin, in C3H10T1/2 (10T1/2) cells. Electrophoretic mobility shift assays demonstrated changes in the patterns of MEF-2, CACCC, and MEF-3 DNA binding activities following the conversion of 10T1/2 cells into myoblasts and myotubes by stable transfection with a MyoD expression vector. In particular, MEF-2 binding activity was up-regulated in 10T1/2 cells stably transfected with a MyoD expression vector only after these cells fused and differentiated into skeletal myotubes. Taken together, these results demonstrated that distinct lineage-specific transcriptional regulatory elements control the expression of a single myofibrillar protein gene in fast skeletal and cardiac muscle. In addition, they show that bHLH transcription factors can indirectly transactivate the expression of some muscle-specific genes.

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Lin, Yixin, Qin Fu, Jie Zhu, Julie M. Miller et Jennifer E. Van Eyk. « Development of a Qualitative Sequential Immunoassay for Characterizing the Intrinsic Properties of Circulating Cardiac Troponin I ». Clinical Chemistry 56, n^o 8 (1 août 2010) : 1307–19. http://dx.doi.org/10.1373/clinchem.2009.135186.

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BACKGROUND With myocardial infarction (MI), cardiac troponin is released from the heart into circulation, where it can be detected with immunoassays independently quantifying cardiac troponin I (cTnI) or cTnT. There is, however, no single immunoassay that sequentially probes the posttranslational modification status of cTnI or directly characterizes whether circulating cTnI is bound to cTnC and/or cTnT. Here we describe the development of a qualitative immunoassay to directly probe the primary and ternary structure of circulating cTnI through diffractive optics technology (dotLab® System, Axela). METHODS Anti-cTnI antibody 8I-7 was immobilized on a patterned sensor to capture cTnI. One or more detector antibodies were sequentially introduced to probe for amino acid sequence integrity or phosphorylation status of cTnI, or its association with cTnC and/or cTnT. Respective immunocaptures were recorded as real-time diffractive intensities (DIs), and the DI differences were analyzed. Each immunodetection was independent of the others but was done in a single sequential assay. RESULTS This diffraction-based immunoassay successfully characterized cTnI. The unamplified assay determined whether cTnI was degraded at N-terminus and/or C-terminus or phosphorylated. Sequential application of multiple detector antibodies without an antibody-stripping step enables real-time interrogation of 5 different epitopes of cTnI, or direct detection of the cTn complex (cTnI–cTnC–cTnT) in a single sequential assay. Finally, this assay was optimized with amplification to directly detect circulating cTnI bound to cTnC and cTnT in serum from an MI patient. CONCLUSIONS The dot® Immunoassay is the first qualitative sequential immunoassay to address the direct interactions of the troponin subunits and various modified forms of cTnI.

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Ren, Xiaoming, et Guangming Zhu. « A variable stiffness morphing skin : preparation and properties ». Smart Materials and Structures 30, n^o 12 (9 novembre 2021) : 125016. http://dx.doi.org/10.1088/1361-665x/ac32e8.

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Abstract In the course of flight, morphing skins play an important role in morphing aircrafts. Shape memory polymer (SMP) with variable stiffness performance is a good candidate material for skin. In this paper, a series of SMP morphing skins were prepared from hydro-epoxy resin, carboxyl-terminated butadiene acrylonitrile (CTBN) and maleic anhydride. By adjusting molecular weight and content of CTBN, in-plane properties and out-of-plane properties of morphing skins can be adjusted. Due to the in-plane tensile stress acting on the skin during flight, tensile test was carried out to study its in-plane performance. After testing, skin can resist maximum in-plane tensile strength of 63.7 MPa. As for the out-of-plane performance of the skin, shape memory test was studied in this paper. All morphing skins have 100% shape fixity rate (Rf) and fast shape recovery rate (Rr). When toughened by CTBN of 10% of 4000 molecular weight with a mass fraction, the skin can recover its out-of-plane deformed shape in 33 s. The SMP skins were proved to be a promising candidate for morphing skins.

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Gollapudi, Sampath K., et Murali Chandra. « Cardiomyopathy-Related Mutations in Cardiac Troponin C, L29Q and G159D, Have Divergent Effects on Rat Cardiac Myofiber Contractile Dynamics ». Biochemistry Research International 2012 (2012) : 1–11. http://dx.doi.org/10.1155/2012/824068.

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Previous studies of cardiomyopathy-related mutations in cardiac troponin C (cTnC)—L29Q and G159D—have shown diverse findings. The link between such mutant effects and their divergent impact on cardiac phenotypes has remained elusive due to lack of studies on contractile dynamics. We hypothesized that a cTnC mutant-induced change in the thin filament will affect global myofilament mechanodynamics because of the interactions of thin filament kinetics with bothCa2+binding and crossbridge (XB) cycling kinetics. We measured pCa-tension relationship and contractile dynamics in detergent-skinned rat cardiac papillary muscle fibers reconstituted with the recombinant wild-type rat cTnC (cTnCWT),cTnCL29Q, andcTnCG159Dmutants.cTnCL29Qfibers demonstrated a significant decrease inCa2+sensitivity, butcTnCG159Dfibers did not. Both mutants had no effect onCa2+-activated maximal tension. The rate of XB recruitment dynamics increased incTnCL29Q(26%) andcTnCG159D(25%) fibers. The rate of XB distortion dynamics increased incTnCG159Dfibers (15%). Thus, thecTnCL29Qmutant modulates the equilibrium between the non-cycling and cycling pool of XB by affecting theon/offkinetics of the regulatory units (Tropomyosin-Troponin); whereas, thecTnCG159Dmutant increases XB cycling rate. Different effects on contractile dynamics may offer clue regarding howcTnCL29QandcTnCG159Dcause divergent effects on cardiac phenotypes.

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Wang, Y. P., et F. Fuchs. « Length, force, and Ca(2+)-troponin C affinity in cardiac and slow skeletal muscle ». American Journal of Physiology-Cell Physiology 266, n^o 4 (1 avril 1994) : C1077—C1082. http://dx.doi.org/10.1152/ajpcell.1994.266.4.c1077.

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Troponin C occurs as two isoforms, one (sTnC) expressed in fast skeletal muscle and the other (cTnC) expressed in cardiac and slow skeletal muscle. On the basis of subunit exchange experiments it has been suggested that cTnC may play a specific role as a length-sensing molecule. In this study we have compared skinned fibers from bovine ventricle and slow rabbit soleus muscle with respect to the effects of force and sarcomere length on Ca2+ binding to troponin C. A double-isotope technique was used to measure Ca2+ binding concurrent with force generation. The phosphate analogue vanadate was used to regulate force independent of free Ca2+ concentration. To determine the effect of sarcomere length, muscle fibers were released from longer sarcomere length to shorter sarcomere length, and bound Ca2+ was determined either before or after the release. Reduction in force or length was associated with reduced binding of Ca2+ to cTnC in cardiac muscle, but no effect of these interventions was seen in soleus muscle. Thus the nature of the mechanical feedback on the regulatory Ca(2+)-binding sites appears to be a property of the myofilament system rather than the troponin C isoform.

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Heng, Zhengguang, Yang Chen, Huawei Zou et Mei Liang. « Simultaneously enhanced tensile strength and fracture toughness of epoxy resins by a poly(ethylene oxide)-block-carboxyl terminated butadiene-acrylonitrile rubber dilock copolymer ». RSC Advances 5, n^o 53 (2015) : 42362–68. http://dx.doi.org/10.1039/c5ra05124j.

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Santos, André M., Paulo V. Peixoto, Mariana S. D'Ávila, Tiago C. Peixoto, Ticiana N. França, Samay Z. R. Costa, Gabriela C. Cid et Vivian A. Nogueira. « Troponina C na detecção imuno-histoquímica de alterações regressivas precoces no miocárdio de bovinos e ovinos intoxicados por monofluoroacetato de sódio ». Pesquisa Veterinária Brasileira 36, n^o 2 (février 2016) : 67–72. http://dx.doi.org/10.1590/s0100-736x2016000200001.

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Resumo: Ao que tudo indica, o monofluoroacetato de sódio (MF) é o princípio tóxico das numerosas plantas que causam "morte súbita" no Brasil. Eventualmente, observam-se, nos animais intoxicados por MF, grupos de cardiomiócitos com aumento da eosinofilia citoplasmática. Essas alterações cardíacas, no entanto, na maioria dos casos, ainda são incipientes, de difícil interpretação, não há reação inflamatória e devem ser diferenciadas de artefato. O presente trabalho teve como objetivo detectar a presença de alterações regressivas precoces no miocárdio de bovinos e ovinos intoxicados experimentalmente por MF, através da imuno-histoquímica com troponina C (cTnC). Fragmentos de coração de seis bovinos (três que receberam, por via oral, doses únicas de 0,5mg/kg e, os demais, 1,0mg/kg de MF) e cinco ovinos (um recebeu, por via oral, dose única de 0,5mg/kg, outros dois receberam doses de 1,0mg/kg; um ovino recebeu, por via oral, doses subletais repetidas diariamente de 0,1mg/kg/dia, por quatro dias, e outro, 0,2mg/kg/dia por seis dias) foram submetidos à técnica de imuno-histoquímica com anticorpo anti-cTnC. Nos cardiomiócitos dos bovinos e ovinos verificou-se redução dos níveis de expressão da cTnC no citoplasma de grupos de fibras musculares. Diminuição significativa na imunorreatividade ocorreu, sobretudo, em cardiomiócitos que apresentavam, no exame histopatológico, aumento da eosinofilia citoplasmática. A diminuição ou ausência da expressão da cTnC nos animais intoxicados por MF permitiu estabelecer a diferença entre necrose coagulativa de cardiomiócitos e artefato ocasionado pelo fixador. Isso indica que este método pode ser utilizado com segurança para identificação de lesões regressivas precoces, ou não, no miocárdio, independentemente da causa. Adicionalmente, é possível afirmar que, dependendo do tempo de evolução, a toxicose por MF, bem como por plantas causadoras de "morte súbita" em bovinos e ovinos, podem cursar com lesões necrotizantes no miocárdio.

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Gillis, Todd E., Bo Liang, Franca Chung et Glen F. Tibbits. « Increasing mammalian cardiomyocyte contractility with residues identified in trout troponin C ». Physiological Genomics 22, n^o 1 (16 juin 2005) : 1–7. http://dx.doi.org/10.1152/physiolgenomics.00007.2005.

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The Ca2+ sensitivity of force generation in trout cardiac myocytes is significantly greater than that from mammalian hearts. One mechanism that we have suggested to be responsible, at least in part, for this high Ca2+ sensitivity is the isoform of cardiac troponin C (cTnC) found in trout hearts (ScTnC), which has greater than twice the Ca2+ affinity of mammalian cTnC (McTnC). Here, through a series of mutations, the residues in ScTnC responsible for its high Ca2+ affinity have been identified as being Asn2, Ile28, Gln29, and Asp30. When these residues in McTnC were mutated to the trout-equivalent amino acid, the Ca2+ affinity of the molecule, determined by monitoring the fluorescence of a Trp inserted for a Phe at residue 27, is comparable to that of ScTnC. To determine how a McTnC mutant containing Asn2, Ile28, Gln29, and Asp30 (NIQD McTnC) affects the Ca2+ sensitivity of force generation, endogenous cTnC in single, chemically skinned rabbit cardiomyocytes was replaced with either wild-type McTnC or NIQD McTnC. Our results demonstrate that the cardiomyocytes containing NIQD McTnC were approximately twice as sensitive to Ca2+, illustrating that a McTnC mutant with similar Ca2+ affinity as ScTnC can be used to sensitize mammalian cardiac myocytes to Ca2+.

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Yang, Zhen, Guoyi Zhuang, Xiaoshu Wei, Jintao Wei, Huayang Yu et Wei Xu. « Quantitative Analysis of the Blending Degree of Virgin and RAP Binders in Recycled Asphalt Mixtures with a High RAP Content ». Applied Sciences 8, n^o 12 (18 décembre 2018) : 2668. http://dx.doi.org/10.3390/app8122668.

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Recycled asphalt mixtures (RAM), which are prepared by blending reclaimed asphalt pavement (RAP), virgin bitumen and mineral additives, provide a variety of advantages, including resource recycling, reductions in costs, and reduced negative environmental impacts. However, multiple agencies have expressed concerns about the utilization ratio of RAP; thus, a comprehensive understanding of the blending degree of virgin and RAP binders in RAM would be significantly helpful for promoting the application of RAP. This study aims to quantitatively analyze the blending degree of virgin and RAP binders in RAM with high RAP contents. Carboxyl-terminated butadiene acrylonitrile (CTBN) was utilized as a tracer to mark the virgin bitumen; in addition, Fourier transform infrared (FTIR) spectroscopy was used to develop the structural index of CTBN (ICTBN). By establishing the standard curve between ICTBN and the CTBN content, the blending degree of virgin and RAP binders at different locations within RAM can be determined quantitatively. The study results indicate that the RAP binder was completely blended with the virgin bitumen in the outer RAP layer. However, the blending degree decreased with an increase in the RAP depth, and the blending degree in the inner RAP layer was only approximately half that which was found in the case of complete blending.

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Bagheri, R., et R. A. Pearson. « Interfacial studies in CTBN-modified epoxies ». Journal of Applied Polymer Science 58, n^o 2 (10 octobre 1995) : 427–37. http://dx.doi.org/10.1002/app.1995.070580221.

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Guo, Yifan, Junjie Zheng, Rongjun Zhang et Youbin Yang. « AN EVIDENCE-BASED RISK DECISION SUPPORT APPROACH FOR METRO TUNNEL CONSTRUCTION ». JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 28, n^o 5 (3 mai 2022) : 377–96. http://dx.doi.org/10.3846/jcem.2022.16807.

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The risk-informed decision-making of metro tunnel project is often faced with the problem of inadequate utilization of available information. In order to address the epistemic uncertainty problem caused by insufficient utilization of information in decision-making, this paper proposes a risk decision support approach for metro tunnel construction based on Continuous Time Bayesian Network (CTBN) technique. CTBN can factor the state space of variables in tunnel projects and perform evidence-based reasoning, which enables the diverse information of expert opinions, project-specific parameters, historical data and engineering anomalies to be the evidence to support decision-making. A concise CTBN model development method based on Dynamic Fault Trees is presented to replace the cumbersome model learning process. The proposed approach can utilize multi-source information as evidence to provide multi-form decision support both in the pre-construction stage and construction stage of the tunnel construction project, and the results can support the decisions on judging the acceptability of the risk, developing response strategies for risk factors and diagnosing the causes of the hazardous event. A case study on the water leakage risk of tunnel construction in China is presented to illustrate the feasibility of the approach. The case study shows that the approach can assist in making informed decisions, so as to improve the engineering safety.

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Zhang, Haiyang, Qin Qu et Yang He. « Fracture toughness of CTBN modified PF particleboard based on equal deflection rigidity ». MATEC Web of Conferences 275 (2019) : 01021. http://dx.doi.org/10.1051/matecconf/201927501021.

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The fracture toughness of particleboard should be evaluated when it was intended to use in the structure system. Single edge notched beam (SENB) test method was employed to measure stress intensity factor (SIF) of the internal middle layer of the PF and CTBN modified PF particleboard. Equal deflection rigidity algorithm (EDRA) was used to homogenized the sandwich bi-material beam in order to make the test procedure match ASTM E399-2017. The results shown that the optimized CTBN addition was among 8% to 12% and the improve ratio of SIF of the particleboard middle layer was 27.27 %. Owing to the different broken mechanism, the tested fracture performance show more stability compared to the traditional internal bonding (IB) test. But the fracture test strongly depend on the notched incision morphology.

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LIPSCOMB, Simon, Laura C. PRESTON, Paul ROBINSON, Charles S. REDWOOD, Ian P. MULLIGAN et Christopher C. ASHLEY. « Effects of troponin C isoform on the action of the cardiotonic agent EMD 57033 ». Biochemical Journal 388, n^o 3 (7 juin 2005) : 905–12. http://dx.doi.org/10.1042/bj20041841.

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The effects of the cardiotonic potentiator EMD 57033 on different TnC (troponin C) isoforms were investigated. Endogenous skeletal TnC was extracted from glycerinated, permeabilized rabbit psoas fibres and replaced with either purified native rabbit psoas TnC (fast TnC) or human recombinant cTnC (cardiac TnC) (3 mg/ml in relaxing solution for 30 min). In both conditions, 10 μM EMD 57033 increased maximal calcium-activated force (Pmax) and gave a leftward shift in the pCa–tension curve. With cTnC, the increase in Pmax was much greater (228%) compared with the effect seen for fast TnC (137%), which was the same as that in unextracted control fibres. When the whole troponin was replaced rather than just TnC, the effects of EMD 57033 on fibres replaced with cTn were the same as with the cTnC subunit alone, except that the force at low Ca2+ concentrations was not increased as much. If TnC was only partially extracted, it was found that the degree of extraction did not influence the effect of EMD 57033, except when force was decreased to below 10% of the pre-extraction Pmax. Dynamic stiffness was not altered by EMD 57033 in any of the preparations. The rate of tension recovery following a release–restretch method (ktr) was decreased by EMD 57033. We conclude that EMD 57033 acts by a rate-modulating effect, and that the quantitative response of this effect is dependent on the TnC isoform present.

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Konnola, Raneesh, Jinu Joji, Jyotishkumar Parameswaranpillai et Kuruvilla Joseph. « Structure and thermo-mechanical properties of CTBN-grafted-GO modified epoxy/DDS composites ». RSC Advances 5, n^o 76 (2015) : 61775–86. http://dx.doi.org/10.1039/c5ra10599d.

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Carboxyl terminated poly(acrylonitrile-co-butadiene) (CTBN) is grafted on to graphite oxide (GO) to prepare GCTBN in order to improve the dispersion and interfacial bonding between GO and epoxy resin in an epoxy/DDS system.

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Bessa, Kelly, et Fernando Fernandes Oliveira. « CORPORAÇÕES E PRÁTICAS DE ORDENAMENTO TERRITORIAL : A CONSTRUÇÃO E A RECONSTRUÇÃO DAS ESPACIALIDADES DA CTBC (HOLDING ALGAR) ». Caminhos de Geografia 9, n^o 28 (5 janvier 2009) : 201–20. http://dx.doi.org/10.14393/rcg92815787.

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Este texto objetiva analisar as práticas socioespaciais de ordenamento territorial da CTBC, carro-chefe da holding Algar, enfatizando a construção e a reconstrução de suas espacialidades, antes da estatização e depois da privatização das telecomunicações no Brasil.

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Gardner, Melissa, Giuliana Zarrella, Jorg Dietrich et Michael Parsons. « NCOG-48. LONGITUDINAL ASSESSMENT OF SUBJECTIVE COGNITIVE FUNCTION IN A BRAIN TUMOR SAMPLE : IMPROVED CORRESPONDENCE WITH NEUROPSYCHOLOGICAL PERFORMANCE OVER TIME ». Neuro-Oncology 23, Supplement_6 (2 novembre 2021) : vi162. http://dx.doi.org/10.1093/neuonc/noab196.637.

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Abstract INTRODUCTION Estimates of subjective cognitive function (SCF) generally show minimal correlation with objective measures of neurocognitive function (NCF). Our group recently validated a new metric of SCF in neuro-oncology patients, creating the Cognitive Index of the Functional Assessment of Cancer Therapy-Brain (FACT-Br-CI). This study examines whether brain tumor (BT) patients evaluated on more than one occasion show improved relationship between SCF and NCF. We hypothesized that change scores in SCF and NCF across evaluation would be more highly correlated than SCF and NCF at either timepoint. METHODS A retrospective study of BT patients who completed two neuropsychological evaluations (baseline, follow-up) was conducted. NCF was measured by the clinical trial battery composite (CTBC), a mean of 6 commonly used neuropsychological test scores. SCF was measured by the FACT-Br-CI. Mood/Anxiety were measured by the Beck scales (BAI/BDI-II). Change over time on each metric was evaluated with paired t-test. Correlational analyses evaluated relationships between NCF, SCF, and mood within and between time points. RESULTS Twenty-nine patients (16 female; mean age=54.6y; mean education=15.5y) completed all CTBC measures and FACT-Br-CI, 28 of whom completed and BDI and/or BAI. On group analyses, there were no significant differences between baseline and follow-up on CTBC (t=-.53;p=ns) or FACT-Br-CI (t=-.98;p=ns). Correlations between CTBC and FACT-Br-CI were nonsignificant at baseline (r=.24;p=ns), but significant at follow-up (r=.56;p=0.002). Change scores over time were unrelated (r=-.104;p=ns). Similar to previous studies, the FACT-BR-CI correlated with the BDI-II at baseline (r=-.38;p=0.04) and follow-up (r=-.59;p< 0.001) and with the BAI at follow-up (r=-.44;p=0.02). CONCLUSION In this small group of brain tumor patients seen for repeated neuropsychological evaluations, we found that agreement between SCF and NCF was much higher on their second than initial evaluation. These findings suggest that patients may develop enhanced awareness of their cognitive function from an initial evaluation that persists over time.

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Peyser, Paul, et Yitchak Steg. « The Fracture Behavior of CTBN Modified Epoxy ». Journal of Adhesion 25, n^o 2 (avril 1988) : 133–44. http://dx.doi.org/10.1080/00218468808071255.

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Wibowo, Muhammad Ponco, et Siti Ita Rosita. « Analisis Penerapan PSAK 71 Dalam Penyajian Cadangan Kerugian Penurunan Nilai Dan Kinerja Keuangan Perusahaan Perbankan ». Jurnal Ilmiah Akuntansi Kesatuan 8, n^o 2 (12 août 2020) : 147–56. http://dx.doi.org/10.37641/jiakes.v8i2.373.

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In 2020 companies in Indonesia have to implement PSAK 71 to replace PSAK 55. With the forward looking Expected Credit Loss approach in PSAK 71, profit of the banking industry has the potential to be declining because banks have to prepare Allowance for Impairment Losses since the initial recognition of financial assets. This study aims to find out the application of PSAK 71 in the presentation of allowance for impairment losses on banking companies in Indonesia and examine its financial performance using the CAMEL method. This research was conducted at CTBC Bank of Indonesia The type of data used in this study is secondary data which was obtained in the form of annual reports containing audit reports and other additional information. The analysis of the data is intended to find out whether the presentation of allowance for impairment losses at CTBC Bank is in accordance with PSAK 71 or not, and analyze the company’s financial performance The results of this study show that CTBC Bank of Indonesia has implemented PSAK 71 of allowance for impairment losses properly and the recalculation of impairment losses was in accordance with transitional provisions of PSAK 71 in 2017. This reduced the value of Bank’s CAMEL by 3,33 resulting from the decrease of net income and total assets. However, as of December 31, 2018 the company has succeeded in raising the CAMEL value to 85,55 and achieved a rating of healthy status from Bank Indonesia Keywords:PSAK 71, Impairment losses, CAMEL, financial instrument

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Ma, Shi Ning, Nai Shu Zhu, C. Q. Li et C. H. Hu. « Study on Preparation and Properties of a Room Temperature Fast Curing Epoxy Resin Nano-Adhesive ». Key Engineering Materials 373-374 (mars 2008) : 662–65. http://dx.doi.org/10.4028/www.scientific.net/kem.373-374.662.

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A room temperature fast curing epoxy resin nano-adhesive was prepared and modified by nano-SiO2 and liquid rubber CTBN. It shows good shear strength value and heat-durability and also meets the conditions of room temperature and short solidified time. Compared with conventional resin mixing method, adhesive modified by nanomaterial can achieve better heat-durability. Compound cation/nonionic surfactants were used for modifying nano-SiO2 and solution mix method was used for preparation of nano-SiO2 epoxy resin adhesive. The effects of nano-SiO2 to adhesive’s mechanical property and heat-durability were investigated. Adhesive with 2wt% nano-SiO2 shows improved properties which shear strength value is 17.9 MPa and vitrification point is 216.5°C. Micropores and grains of nano-SiO2/liquid rubber CTBN modifying system were observed using scanning electron microscope. Adhesives were investigated using infrared spectroscopy analysis. Nano-SiO2 modified using compound surfactant has higher reacting activity and accelerates the reaction of adhesive. It can be used as catalyst.

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Liang, Bo, Franca Chung, Yang Qu, Dmitri Pavlov, Todd E. Gillis, Svetlana B. Tikunova, Jonathan P. Davis et Glen F. Tibbits. « Familial hypertrophic cardiomyopathy-related cardiac troponin C mutation L29Q affects Ca2+ binding and myofilament contractility ». Physiological Genomics 33, n^o 2 (avril 2008) : 257–66. http://dx.doi.org/10.1152/physiolgenomics.00154.2007.

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The cardiac troponin C (cTnC) mutation, L29Q, has been found in a patient with familial hypertrophic cardiomyopathy. We previously showed that L29, together with neighboring residues, Asp2, Val28, and Gly30, plays an important role in determining the Ca2+ affinity of site II, the regulatory site of mammalian cardiac troponin C (McTnC). Here we report on the Ca2+ binding characteristics of L29Q McTnC and D2N/V28I/L29Q/G30D McTnC (NIQD) utilizing the Phe27 → Trp (F27W) substitution, allowing one to monitor Ca2+ binding and release. We also studied the effect of these mutants on Ca2+ activation of force generation in single mouse cardiac myocytes using cTnC replacement, together with sarcomere length (SL) dependence. The Ca2+-binding affinity of site II of L29Q McTnCF27W and NIQD McTnCF27W was ∼1.3- and ∼1.9-fold higher, respectively, than that of McTnCF27W. The Ca2+ disassociation rate from site II of L29Q McTnCF27W and NIQD McTnCF27W was not significantly different than that of control (McTnCF27W). However, the rate of Ca2+ binding to site II was higher in L29Q McTnCF27W and NIQD McTnCF27W relative to control (∼1.5-fold and ∼2.0-fold respectively). The Ca2+ sensitivity of force generation was significantly higher in myocytes reconstituted with L29Q McTnC (∼1.4-fold) and NIQD McTnC (∼2-fold) compared with those reconstituted with McTnC. Interestingly, the change in Ca2+ sensitivity of force generation in response to an SL change (1.9, 2.1, and 2.3 μm) was significantly reduced in myocytes containing L29Q McTnC or NIQD McTnC. These results demonstrate that the L29Q mutation enhances the Ca2+-binding characteristics of cTnC and that when incorporated into cardiac myocytes, this mutant alters myocyte contractility.

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Ochi, Mitsukazu, Masaru Yamauchi, Osamu Kiyohara et Toshio Tagami. « Effect of the addition of aramid-CTBN block copolymer on adhesive properties of cured epoxy resins modified with CTBN ». Journal of Adhesion Science and Technology 9, n^o 12 (janvier 1995) : 1559–73. http://dx.doi.org/10.1163/156856195x00202.

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Labugger, Ralf, Jeremy A. Simpson, Michelle Quick, Heather A. Brown, Christine E. Collier, Irina Neverova et Jennifer E. Van Eyk. « Strategy for Analysis of Cardiac Troponins in Biological Samples with a Combination of Affinity Chromatography and Mass Spectrometry ». Clinical Chemistry 49, n^o 6 (1 juin 2003) : 873–79. http://dx.doi.org/10.1373/49.6.873.

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Abstract Background: Cardiac troponins are modified during ischemic injury and are found as a heterogeneous mixture in blood of patients with cardiovascular diseases. We present a strategy to isolate cardiac troponins from human biological material, by use of affinity chromatography, and to provide samples ready for direct analysis by mass spectrometry. Methods: Cardiac troponins were isolated from human left ventricular tissue by affinity chromatography. Isolated troponins were either eluted and analyzed by Western blot or enzymatically digested while bound to affinity beads. The resulting peptide mixture was subjected to mass spectrometry for protein identification and characterization. The same method was used to analyze serum from patients with acute myocardial infarction (AMI). Results: Affinity chromatography with antibodies specific for one cardiac troponin subunit facilitated the isolation of the entire cardiac troponin complex from myocardial tissue. The three different proteases used for enzymatic digestion increased the total protein amino acid sequence coverage by mass spectrometry for the three cardiac troponin subunits. Combined amino acid sequence coverages for cardiac troponin I, T, and C (cTnI, cTnT, cTnC) were 54%, 48%, and 40%, respectively. To simulate matrix effects on the affinity chromatography–mass spectrometry approach, we diluted tissue homogenate in cardiac troponin-free serum. Sequence coverages in this case were 44%, 41%, and 19%, respectively. Finally, affinity chromatography–mass spectrometry analysis of AMI serum revealed the presence of cardiac troponins in a wide variety of its free and/or complexed subunits, including the binary cTnI-cTnC and cTnI-cTnC-cTnT complexes. Conclusions: Affinity chromatography–mass spectrometry allows the extraction and analysis of cardiac troponins from biological samples in their natural forms. We were, for the first time, able to directly confirm the presence of cardiac troponin complexes in human serum after AMI. This approach could assist in more personalized risk stratification as well as the search for reference materials for cardiac troponin diagnostics.

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Li, King-Lun, Mei Methawasin, Bertrand C. W. Tanner, Henk L. Granzier, R. John Solaro et Wen-Ji Dong. « Sarcomere length–dependent effects on Ca2+-troponin regulation in myocardium expressing compliant titin ». Journal of General Physiology 151, n^o 1 (6 décembre 2018) : 30–41. http://dx.doi.org/10.1085/jgp.201812218.

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Cardiac performance is tightly regulated at the cardiomyocyte level by sarcomere length, such that increases in sarcomere length lead to sharply enhanced force generation at the same Ca2+ concentration. Length-dependent activation of myofilaments involves dynamic and complex interactions between a multitude of thick- and thin-filament components. Among these components, troponin, myosin, and the giant protein titin are likely to be key players, but the mechanism by which these proteins are functionally linked has been elusive. Here, we investigate this link in the mouse myocardium using in situ FRET techniques. Our objective was to monitor how length-dependent Ca2+-induced conformational changes in the N domain of cardiac troponin C (cTnC) are modulated by myosin–actin cross-bridge (XB) interactions and increased titin compliance. We reconstitute FRET donor- and acceptor-modified cTnC(13C/51C)AEDANS-DDPM into chemically skinned myocardial fibers from wild-type and RBM20-deletion mice. The Ca2+-induced conformational changes in cTnC are quantified and characterized using time-resolved FRET measurements as XB state and sarcomere length are varied. The RBM20-deficient mouse expresses a more compliant N2BA titin isoform, leading to reduced passive tension in the myocardium. This provides a molecular tool to investigate how altered titin-based passive tension affects Ca2+-troponin regulation in response to mechanical stretch. In wild-type myocardium, we observe a direct association of sarcomere length–dependent enhancement of troponin regulation with both Ca2+ activation and strongly bound XB states. In comparison, measurements from titin RBM20-deficient animals show blunted sarcomere length–dependent effects. These results suggest that titin-based passive tension contributes to sarcomere length–dependent Ca2+-troponin regulation. We also conclude that strong XB binding plays an important role in linking the modulatory effect of titin compliance to Ca2+-troponin regulation of the myocardium.

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